Documented in Volume 1 of the UNIX Programmers Manual.
% more filename
will list the entire contents of filename at the terminal.
'more' is intended to control terminal formatting by
outputting a screenful at a time. To get another screenful,
type the space bar. To get one more line, type RETURN,
to get help, type 'h'. More is smart (maybe too smart), and
there's lots of help.
% nroff -ms +2 doc.n | more -s
will process the file doc.n through nroff and pipe it to more.
The -s is especially helpful when viewing nroff output, because
it squeezes multiple blank lines, and therefore maximizes the
useful information present on the screen.
Use ' to back up a screenful.
Use :p to back up to the beginning of file.
Use q to quit gracefully (DELETE will work, but may scramble your
terminal I/O).